The present invention relates generally to an implantable medical electrical lead; and more particularly, relates to a lead that includes a common port adapted to receive a guiding device, and further adapted to delivery a contrast medium.
Implantable medical electrical stimulation and/or sensing leads are well known in the fields of cardiac stimulation and monitoring, including cardiac pacing and cardioversion/defibrillation. In the field of cardiac stimulation and monitoring, endocardial leads are placed through a transvenous route to locate one or more sensing and/or stimulation electrodes along or at the distal end of the lead in a desired location within a heart chamber or interconnecting vasculature. In order to achieve reliable sensing of the cardiac electrogram and/or to apply stimulation that effectively paces or cardioverts the heart chamber, it is necessary to accurately position the electrode surface against the endocardium or within the myocardium at the desired site and fix it during an acute post-operative phase until fibrous tissue growth occurs.
The pacemaker or defibrillator implantable pulse generator (IPG) or the monitor is typically coupled to the heart through one or more of such endocardial leads. The proximal end of such a lead is typically formed with a connector that connects to a terminal of the IPG or monitor. The lead body typically comprises one or more insulated conductive wires surrounded by an insulating outer sleeve. Each conductive wire couples a proximal lead connector element with a distal stimulation and/or sensing electrode. An endocardial cardiac lead having a single stimulation and/or sensing electrode at the lead distal end and a single conductive wire is referred to as a unipolar lead. An endocardial cardiac lead having two or more stimulation and/or sensing electrodes at the lead distal end and two or more conductive wires is referred to as a bipolar lead or a multi-polar lead, respectively.
In order to implant an endocardial lead within a heart chamber, a transvenous approach is utilized wherein the lead is inserted into and passed through the subclavian, jugular, or cephalic vein and through the superior vena cava into the right atrium or ventricle. An active or passive fixation mechanism is incorporated into the distal end of the endocardial lead and deployed to maintain the distal end electrode in contact with the endocardium position.
More recently, endocardial pacing and cardioversion/defibrillation leads have been developed that are adapted to be advanced into the coronary sinus and coronary veins branching there from in order to locate the distal electrode(s) adjacent to the left ventricle or the left atrium. The distal end of such coronary sinus leads is advanced through the superior vena cava, the right atrium, the valve of the coronary sinus, the coronary sinus, and may further be advanced into a coronary vein communicating with the coronary sinus, such as the great vein. Typically, coronary sinus leads do not employ any fixation mechanism and instead rely on the close confinement within these vessels to maintain each electrode at a desired site.
Routing an endocardial lead along a desired path to implant the electrode or electrodes in a desired implantation site, either in a chamber of the heart or in the selected cardiac vein or coronary artery, can be difficult. This is particularly true for steering leads through the coronary sinus and into a branching vein on the left myocardium. Anomalies in the vascular anatomy and the number of branch veins associated with the anatomy make locating the desired path challenging.
Several common approaches have been developed to place electrodes at a desired implant site, such as within the left side of the heart. According to one approach, a guide catheter is steered into the desired location in the vasculature. A lead is then fed through the inner lumen of the catheter such that the lead electrode(s) are positioned at predetermined locations. The guide catheter may then be withdrawn. This type of approach is described in commonly assigned U.S. Pat. Nos. 6,006,137, 5,246,014, and 5,851,226 incorporated herein by reference. The described systems employ highly flexible, catheters surrounding the lead body.
When using a guide catheter, it may be difficult to locate a desired implant site within the torturous curves of the venous system. This is particularly true if the implant site is located within the coronary sinus or one of the branch veins. To aid in locating the desired implant site, radiopaque dye may be injected into the venous anatomy so that the coronary veins are visible using a fluoroscopic device. This procedure, sometimes referred to as a xe2x80x9cvenogramxe2x80x9d, allows the surgeon to determine the appropriate path to be followed when performing the implant.
Venograms may be performed using a catheter having a lumen for delivering contrast medium such as fluoro-visible dye into a patient""s vascular system. A fluoroscopy device may then be used to create a map of the patient""s cardiac vasculature so that a pacing or defibrillation electrode may be steered to an implant site. Such a system is described in U.S. Pat. No 6,122,522 to Tockman which describes a guide catheter having a balloon on a distal tip. Prior to the dye-injection procedure, the balloon is inflated to temporarily occlude the backflow of blood through a vessel so that the dye is retained within the vessels long enough to obtain the venogram. After a venogram is taken, the balloon is deflated to allow a guidewire to be passed through a central lumen of the catheter and into the appropriate venous pathway. The guide catheter is then withdrawn from the venous system and a pacing lead is advanced over the guidewire for placement at the implant site.
One disadvantage of the system described in the ""522 patent is that once the catheter is withdrawn, another venogram can not readily be obtained. Thus, if the surgeon encounters difficulty in placing the lead, the guidewire and lead must be withdrawn, and the catheter re-inserted within the vasculature. This is time consuming and increases the risk of venous perforation.
U.S. Pat. No. 5,755,766 to Chastain discloses a lead having a lumen adapted to receive a guidewire. If desired, the guidewire may be withdrawn from the lumen so that the lumen may be utilized to deliver contrast medium. If it is determined that the lead must be re-positioned, the guidewire must be re-inserted and the process repeated. This both lengthens and complicates the implant procedure.
What is needed, therefore, is a system and method that allows a venogram to be obtained while a lead and guidewire is still in place within the vasculature. Ideally, the lead is adapted and sized to allow for placement and use within coronary arteries and cardiac veins such as the veins in the left-side of the heart, including the coronary sinus and branch veins associated with the coronary sinus.
A medical electrical lead is disclosed having an inner lumen adapted to receive a stiffening member, and which is further adapted to deliver fluoro-visible media while the stiffening member is located within the inner lumen. According to one aspect of the invention, the stiffening member is a guide wire having an inner lumen. The lumen of the guide wire is used to deliver the contrast medium while the guide wire is in place within the lumen of the lead. Delivery of the contrast medium may also occur while the distal tip of the guide wire is advanced past the distal tip of the lead, or while the guide wire remains retracted within the lumen of the lead. In another embodiment, a stiffening member that is sized to occupy only a portion of the lumen of the lead is utilized, with the non-occupied portion of the lumen being large enough to deliver fluoro-visible medium from an injection port at the proximal end of the lead to a delivery port at the distal end of the lead.
The lumen of the lead and/or any inner lumen of the stiffening member may be coated with an anti-inflammatory agent to prevent infection due to bodily fluids contacting the lumen(s). Alternatively, these lumens may be coated partially, or entirely, with a lubricious material that both facilitates the injection of the viscous dye medium, and also allows the stiffening member to be advanced more readily within the lead body.
In one embodiment, the lead includes a sealable member located at the distal end of the lumen of the lead to prevent the ingress of bodily fluids within this lumen. The sealable member includes an opening to allow the stiffening member to be advanced outside of the lead lumen. In one embodiment, the sealable member is a flexible membrane including at least one opening to allow for passage of the stiffening member. In another embodiment, the sealable member includes multiple flap-like structures that seal around a stiffening member advanced distally of the lead body. The flap-like structures may overlap when in the closed position, and may be constructed with a preferential bending direction so that they tend to open distal to the lead body.
In another embodiment, sealable member is a cup-shaped seal element located distal to an electrode, and having a pre-pierced opening to define a path for passage of the guide wire. The seal element is adapted to allow for radial expansion of the seal during passage of the guide wire, while still ensuring that the electrode makes contact with body tissue. In yet another embodiment, the seal element is located within the electrode rather than extending distally of it. The electrode of this configuration is provided with diametrically opposed openings to allow the electrode to spread during passage of a guide wire therethrough.
The lead of the current invention may be placed using a guide catheter as is known in the art. In one embodiment of the invention, the guide catheter includes an inflatable member that may be inflated to at least partially occlude a vessel prior to the delivery of the contrast medium within the vessel. This prevents the contrast media from being flushed from the vessel before a venogram may be obtained. In another embodiment, the lead of the current invention includes an inflatable member and an inflation lumen in fluid communication with the inflatable member. The inflatable member may be inflated prior to delivery of the contrast media.
Other aspects of the current invention will become apparent to those skilled in the art from the following detailed description, and the accompanying figures.